Laser Diode Assembly and Method for Producing a Laser Diode Assembly

ABSTRACT

A laser diode arrangement having at least one semiconductor substrate, having at least two laser stacks each having an active zone and having at least one intermediate layer. The laser stacks and the intermediate layer are grown monolithically on the semiconductor substrate. The intermediate layer is arranged between the laser stacks. The active zone of the first laser stack can be actuated separately from the active zone of the at least one further laser stack.

The present invention relates to a laser diode arrangement having asemiconductor substrate, having laser stacks and intermediate layersbetween the laser stacks. Furthermore, a method for producing a laserdiode arrangement is specified.

In the prior art, current is applied uniformly to laser diodes of alaser diode arrangement. This means that the light outputs of thedifferent laser diodes of the laser diode arrangement cannot be variedindependently of one another.

This problem is solved by a laser diode arrangement and a method forproducing a laser diode arrangement in accordance with the independentclaims 1 and 14 respectively.

Developments and advantageous implementations of the laser diodearrangement and of the method for producing a laser diode arrangementare set down in the dependent claims.

EXEMPLARY EMBODIMENTS

Different embodiments have a laser diode arrangement having at least onesemiconductor substrate. At least two laser stacks each having an activezone and having at least one intermediate layer are provided. The laserstacks and the intermediate layers area are grown monolithically on thesemiconductor substrate. The intermediate layers are arranged betweenthe laser stacks. The active zone of the first laser stack can beactuated separately from the active zone of the at least one furtherlaser stack.

The semiconductor substrate can be a III-V compound semiconductormaterial, in particular a nitride compound semiconductor material suchas gallium nitride (GaN) and aluminum nitride (AlN). Alternatively,gallium arsenide (GaAs), silicon carbide (SiC) or sapphire can beemployed as the substrate.

Silicon (Si) can also be used as the semiconductor substrate.

The active zones can be pn junctions, double heterostructure, multiplequantum well structure (MQW), single quantum well structure (SQW).Quantum well structure means: quantum wells (2-dim), quantum wires(1-dim) and quantum dots (O-dim). The current is injected into theactive zone through a p-doped layer and through an n-doped layer.

As described above, the active zone can be a multiple quantum wellstructure. It consists of a plurality of active layers. A barrier layerlies between the active layers in each case. Diffusion barriers reducethe danger of p-dopant of the p-doped confinement layer penetrating intothe active zone.

In each case a further barrier layer precedes the first active layer andfollows the last active layer in the growth direction. The active layerscontain or consist of InGaN and are between about 0.8 nm and about 10 nmthick. The barrier layers contain or consist ofAl_(x)In_(y)Ga_((1-x-y))N where 0≦(x+y)≦1 and/or GaN and are between 1and 200 nm thick.

The monolithic growth means that the plurality of laser stacks are grownin succession on the same wafer. In particular, no laser bars aremounted one above the other by soldering or adhesive means.

In the present invention, the layer sequences are grown onto one anotherby means of molecular beam epitaxy or metal organic vapor phase epitaxyor vapor phase epitaxy or liquid phase epitaxy.

The monolithic growth of the laser stacks is advantageous because itmeans that particularly small spacings of the active zones and the laserdiodes which can be formed from them can be implemented. Withoutmonolithic growth, arrangements consisting of laser diodes would berestricted to a minimum vertical spacing of the laser diodes from oneanother of about 100 μm. This minimum spacing derives from the minimumthickness to be processed of the laser diode structures. This widespacing of the laser diode structures arranged vertically above oneanother limits the maximum optical power density which can be achievedand also the etendue.

The essential aspect of the invention is the fact that the laser diodesfrom different active zones can be actuated separately. This means thatin addition to the intensity, it is also possible to dynamically alterthe color point of the emitted radiation.

In a preferred embodiment of the invention, the active zones areactuated through separate n-contacts and separate p-contacts. In thissituation, in order to generate the primary colors blue, green and redeach active zone is connected to a separate n-contact and a separatep-contact. The laser stacks are connected to one another by way of anintermediate layer. This results in flexibility as desired in regard tocontacting the single light sources and the parasitic co-illumination ofother light sources in the laser stack is avoided.

In a further preferred embodiment of the invention, the active zones areactuated through a common p-contact and separate n-contacts. The commonp-contact is preferably deposited on a passivation layer and the regionof a heavily doped p-contact layer freed from the passivation layer. Thespace requirement is reduced on account of the separate p-contactsurfaces being dispensed with, which means that components which aremore compact are possible. There is a smaller space requirement on thesemiconductor wafer, which means that the projection light sources canbe produced more cost-effectively. The layer construction is optimizedin regard to parasitic illumination if the band gap of the active zonesin the layer construction increases from bottom to top, in other wordsthe wavelength of the emitted laser light decreases. A further advantageis the fact that the assembly effort is reduced.

In a yet more preferred embodiment of the invention, the active zonesare actuated through a common n-contact and a plurality of separatep-contacts. The common n-contact is preferably deposited on thesubstrate underside. As already in the case of the common p-contact, thespace requirement is reduced. This time, however, as a result of thefact that the separate n-contact surfaces are dispensed with. This makespossible components which are more compact. Moreover there is a smallerspace requirement on the semiconductor wafer, which means that morecost-effective manufacturing is possible. The layer construction isoptimized in regard to parasitic illumination if the band gap of theactive zones decreases from bottom to top, in other words the wavelengthof the emitted laser light increases. A further advantage is the factthat the assembly effort is reduced.

It holds true for all embodiments that the separate n-contacts are ineach case deposited on a highly n-doped contact layer. The separatep-contacts are in each case deposited on a highly p-doped contact layer.

In a preferred embodiment, each laser stack with the associated activezone has at least one laser diode.

In a preferred embodiment of the laser diode arrangement, theintermediate layer is an ohmic resistance. The ohmic contacts can beimplemented as a tunnel diode by means of a monolithic process. Thetunnel junction is also deposited during the epitaxial growth of thelaser structures. It serves to provide the electrical connection. Thetunnel junction comprises two highly doped layers of different conductortypes (n-type or p-type). These two layers are separated from oneanother by means of at least one undoped intermediate layer, for exampleconsisting of Al_(x)In_(y)Ga_((1-x-y))N where 0≦(x+y)≦. The tunneljunction serves to provide the electrical connection for two laserstacks. The laser diodes are connected electrically in series by thetunnel junctions. The tunnel junction or junctions form particularlysmall potential barriers. This facilitates the tunneling of chargecarriers between active zones lying on top of each other.

In the growth direction, the following layer sequence can for exampleresult in the tunnel junction:

-   -   p⁺-type tunnel junction layer    -   middle layer    -   n⁺-type tunnel junction layer.

In an alternative embodiment, the middle layer can be dispensed with inthe tunnel junction. The next laser diode in the stack then follows.

The p⁺-type and/or n⁺-type tunnel junction layer can be designed as asuperlattice. The band gap is smaller in the region of the middle layerthan in the region of the n-type barrier and p-type barrier.

The spatial distance between the regions of high charge carrierdensities (electrons and holes) is small: The tunnel junction has aparticularly low electrical resistance. At the same time, a high chargecarrier density and thus a high tunnel probability can be achieved.

Midgap states in the middle layer of the tunnel junction (can consist ofa homogeneous substance or of: n+-type tunnel junction layer and middlelayer and p+-type tunnel junction layer) are caused by impurity atoms,in particular rare earths and/or transition metals.

In contrast to the usual dopants (Si, Mg), such impurity atoms have theadvantage that they create electronic states which are orderedenergetically approximately in the center of the band gap of the tunneldiode intermediate layer.

Said impurities make it easier for the charge carriers to tunnel throughthe tunnel diode intermediate layer. By this means, the efficiency ofthe tunnel junction is improved compared with a tunnel junction withoutspecifically incorporated impurities.

When the semiconductor body has no tunnel junction, the charge carriersmust overcome high energetic potential barriers during the transitionfrom the n-type confinement layer into the active zone or from thep-doped confinement layer into the active zone. In the case of asemiconductor body having a tunnel junction, such potential barriers donot occur or scarcely occur.

The danger of a non-radiative recombination of electrons is reduced,which particularly in the case of high operating currents, in otherwords in the case of high charge carrier concentrations, increases theefficiency.

With regard to semiconductor bodies having no tunnel junction and havinga multiple quantum well structure, only one of the active zonescontributes to the emission.

The tunnel junction makes it possible to produce the two oppositecontacts of the semiconductor chip from n-type semiconductor material.It is thereby possible to avoid the problem of the low p-typeconductivity of nitride compound semiconductors.

Further advantages of a tunnel layer are as follows:

Only a few contacts are required, namely in the ideal situation only twofor the entire laser diode arrangement. The tunnel layer is extremelythin, namely about 30 nm, in particular thinner than an alternativeinsulating layer. A maximum degree of compactness is therefore possiblewith tunnel diodes. In other words, an ohmic contact is formed betweenthe laser diodes with minimum dimensions.

In a further embodiment, wherein the tunnel junction is situated in thewaveguide layer, the monolithically grown tunnel junction istranslucent. This is particularly advantageous because in the region ofthe laser wavelength the ohmic contact exhibits no or only extremelyslight optical absorption. The laser radiation is advantageouslyscarcely attenuated prior to exiting from the laser diode arrangement.

In a further embodiment of the laser diode arrangement, the intermediatelayer exhibits insulating properties. The insulating layer can be formedby means of ion implantation or by epitaxial growth of a crystallineelectrically insulating layer. The advantage of the crystalline layer isthat the crystalline information is not lost during the further growthprocess. This results in a buffer layer having good crystalline qualityfor overlying layers. There are fewer crystal defects and no newnucleation is required. This means that completely independent controlof the individual active zones with the laser diodes formed from thembecomes possible. The insulating layer is completely transparent to thelaser light. No diffusion of photons or absorption of charge carriersand photons takes place. Two variants of the insulating layer areadvantageous. According to the first variant, the insulator is grownwith intrinsically high purity with an impurity concentration of lessthan 10¹⁷ cm⁻³, preferably less than 10¹⁶ cm⁻³ and especially preferablyless than 10¹⁵ cm⁻³. According to the second variant, the semiconductorcrystals are doped with special dopants which destroy the conductivityof the crystals. In other words, deep centers are produced.

Both the ohmic resistance in the form of a tunnel diode and also theinsulator in the form of a crystalline electrically insulating layer actas the substrate and have the same function as a substrate in thissituation. In other words, they form a good crystalline base for thesubsequent epitaxially grown laser stacks. In a preferred manner, theintermediate layer in the form of a tunnel diode or a crystalline,electrically insulating layer is very similar to the subsequent laserstacks in respect of the lattice properties and the thermal properties.

In a further embodiment, a thin transparent conductive oxide (TCO) layercan be employed as an intermediate layer. In particular, zinc oxide andindium tin oxide (ITO) are advantageous. The TCO layer exhibits a highelectrical conductivity and a suitable transparency for the occurringlaser wavelengths. The TCO layer can be produced in sufficiently goodquality using standard methods such as for example CVD, sputtering oralso MOVPE.

In a preferred embodiment, the active zones are designed such that laserdiodes from different laser stacks emit electromagnetic radiation inwavelength ranges differing from one another. In the case of a III-Vcompound semiconductor system, in particular an InGaN system, as aresult of variation of an indium concentration in the active zones atleast one first laser diode can emit electromagnetic radiation in theblue to UV spectral range, at least one second laser diode can emitelectromagnetic radiation in the green to yellow spectral range and atleast one third laser diode can emit electromagnetic radiation in thered spectral range. It is advantageous in this situation that laserdiodes having different emission spectra are grown monolithically, inother words in a single semiconductor system. The single light sourcesbelonging to each active zone may be present in any sequence. Preferredhowever are stack sequences wherein the most temperature-sensitivelayers are grown last, in other words as the uppermost layer. In theevent that red, green and blue single light sources are grown based onthe AlInGaN material system, it is advantageous to grow theindium-richest red active zone on last.

In preferred embodiments, the active zones in an AlInGaN material systemexhibit the following indium concentrations:

-   -   in the UV range, between about 5% and about 10%,    -   in the blue range, between about 15% and about 25%,    -   in the green range, between about 25% and about 35%,    -   in the yellow range, between about 35% and about 45% and    -   in the red range, greater than about 45%, preferably between 45%        and 60%.

In a preferred embodiment of the invention, the laser diode arrangementis based on two light sources, different laser stacks being grown on twodifferent semiconductor substrates.

For example, an AlInGaN system is grown on a first substrate, e.g. a GaNsubstrate. Active zones for the efficient emission of blue and greenlaser light can thereby be produced. For example, an InGaAlP system isgrown on a second substrate, e.g. a GaAs or GaP substrate. Active zonesfor the efficient emission of yellow to red laser light can thereby beproduced. The two light sources which are grown on the two differentsubstrates can be arranged close to one another. The monolithicallygrown light sources can be arranged beside and/or above one another. Themain advantage consists in increasing the number of colors and thus inenabling the greatest possible adaptation to the theoreticallydisplayable color space. For example, a red light source grown on a GaAssubstrate can be bonded onto a blue and green emitting light source. Inthis situation the metallizations are connected to one another by way ofa solder layer. The active zones from the two different systems exhibita spacing of preferably about 10 μm, especially preferably of less thanabout 5 μm. It is thus possible to achieve spacings such as are achievedin the case of purely monolithic growth without a combination of twolight sources based on two different semiconductor substrates. Thisgrowth on two different substrates with subsequent connection of the twolight sources is particularly cost-effective. This combination of aseparately grown red emitting light source with a separately grown lightsource, with laser emission in the green and blue, is suitable forapplications such as projection, retina scanning display using pocketprojectors, laser TV, video projectors and movie projectors.

In a preferred embodiment of the laser diode arrangement, the laserdiodes are stacked vertically with respect to the semiconductorsubstrate. A monolithic growth process means it is possible to achieve avertical spacing between the laser diodes of less than about 20 μm. Bypreference, the vertical spacing is less than about 5 μm and especiallypreferably less than about 2 μm.

In a preferred embodiment, the laser diodes are arranged horizontally,or in other words parallel, with respect to the semiconductor substrate.A monolithic growth process means it is possible to achieve a horizontalspacing between the laser diodes of less than about 100 μm. Preferablythe horizontal spacing is less than about 20 μm and especiallypreferably less than about 5 μm.

The small spacings of the monolithically grown laser diodes, which liein the order of magnitude of the emission wavelength of theelectromagnetic radiation, are particularly advantageous because thismeans that the light from different laser diodes can be emittedcoherently both temporally and spatially with respect to one another.The individual laser diodes are placed so close together that the wavefields overlap. This is possible below a spacing of the laser diodes ofabout 15 μm. In this case, a phase coupling of the individual emissionstakes place such that a coherent radiation similar to a single laser canbe emitted. This results in further degrees of freedom and capabilitiesfor the interaction between the light waves. This means that it ispossible to achieve a particularly sharp projection image. Thecompactness of the laser diode arrangement means that it can be used inglasses (retina scanning display), mobile telephones, smartphones, PDAsor netbooks (pocket projectors).

The laser diodes can be arranged in a two-dimensional structure. Modesweeping, mode amplification and mode suppression come intoconsideration as an interaction between light waves from different laserdiodes.

Advantageous properties of the present monolithic laser diode structureare the high optical power density with simultaneously reduceddimensions of the laser diode structure. This permits the use of lesscomplicated optical imaging systems, in other words for example a simplelens or a simple lens system. Better imaging properties additionallyresult. The emission takes place from a laser light source, emittinglargely in centric fashion, having an aspect ratio close to 1.

Advantages in the imaging behavior result from this. In a particularlyadvantageous manner the present invention can be used for producingextreme luminances.

Advantageous furthermore are the low production costs (epitaxy,processing and packaging) for the monolithically integrated laser diodearrangements in comparison with the construction of conventional laserarrays having equally strong emission.

In a preferred development of the invention, the layer facing thesemiconductor substrate, which layer adjoins the active zone, is ann-waveguide and the layer facing away from the semiconductor substrate,which layer adjoins the active zone, is a p-waveguide. In other words,in the growth direction the substrate is followed by an n-layer, thencomes an active zone and then in turn a p-layer. This sequence is alsoreferred to as conventional polarity. The deposition of the layersequence can be repeated multiple times. It is advantageous that thisepitaxial structure allows particularly small spacings to be implementedbetween the laser diodes. Monolithically grown components having theabove layer sequence can be operated at high voltages but a lowactuation current. At low current densities however the undesiredquantum-confined Stark effect occurs which distorts the active zone.This results in a poor overlap of the wave functions of the chargecarriers in the laser active zones. Consequently there is a highprobability of non-radiative recombination.

It is advantageous if the layer facing the semiconductor substrate,which layer adjoins the active zone, is a p-waveguide and the layerfacing away from the semiconductor substrate, which layer adjoins theactive zone, is an n-waveguide. In other words, in the growth directionthe substrate is followed by a p-layer, then comes an active zone andthen in turn an n-layer. In this context one also speaks of invertedpolarity or polarity inverted laser diode (PILD). The laser diodearrangement having the above layer sequence can be operated at highvoltages and a low actuation current. The internal piezoelectric fieldoccurring in the case of inverted polarity compensates at leastpartially for other fields, such as for example external fields, andthus contributes towards reducing the quantum-confined Stark effectwhich occurs in particular in crystals having a polar wurztitestructure, such as GaN. This results in improved charge carrierinjection into the active zone; more charge carriers can be trapped inthe active zone. The internal quantum efficiency is then only slightlydependent on the current density. Furthermore, as a result of the lessertransverse conductivity of the p-layers in comparison with the n-layersthe undesired lateral current spreading is significantly reduced. Theelectrical losses are reduced. The lesser transverse conductivity of thep-layers is explained as follows: In comparison with n-layers thep-layer is high impedance. The p-layer is doped with Mg atoms (acceptor)and the n-layer is doped with Si atoms (donor). Doping with Mg atoms at˜10²⁰ cm⁻³ results in a hole concentration of only ˜10¹⁸ cm⁻³.

The lateral current spreading results in an undefined current- andpower-dependent broadening of the current injection. The consequence isan uncontrolled broadening of the luminous spots and thus a reducedluminance. The operating current must be increased because otherwise nopopulation inversion is achieved at the edge of the undefined, currentbroadened region.

In a preferred embodiment of the invention, current shields are providedbetween the laser stacks. These current shields counteract the currentspreading within the monolithically grown laser light source. Throughthe use of current shields it is possible to achieve a situation where amonomode operation can be achieved across the entire monolithic layersystem comprising at least two active zones. The current shield can beproduced by incorporating one or more insulation layers into the layersystem and structuring the insulation layer. Alternatively, a currentshield can be produced by means of ion implantation or by partiallyetching away the contact layer.

Projection systems currently in common use are based on LCD or plasmatechnology or on projectors and video projectors using high-pressurelamps. All these traditional display technologies exhibit a high powerconsumption, a very restricted color space and an extremely limitedservice life. Above all, however, the lack of compactness precludes usein mobile applications such as for example in mobile telephones and inPDAs.

Although RGB projectors based on LED technology overcome somedisadvantages of traditional display systems, it is however possiblewhen using LED projectors to realize sharp projection images only onplane surfaces arranged exactly perpendicular to the projection unit. Inaddition, complex micro-optical systems and imager technologies arerequired and, in addition to increased costs for the overall system,also result in significantly increased dimensions of the LED-based RGBprojectors. A further serious disadvantage of said LED-based RGBprojectors compared with laser-based RGB projectors according to theinvention is the fact that the single light sources arranged beside oneanother for design reasons exhibit a minimum spacing of several hundredμm. This results on the one hand in imaging errors and thus precludesthe highest resolutions. It furthermore renders more difficult theimaging by a single lens system, which limits the compactness of thelight source.

Although laser projectors available today solve the problem of depth offocus and imaging on a not exactly plane surface, they are however notcapable of forming ultracompact RGB laser light sources on account ofthe less than compact dimensions principally of the green laser (greenis produced by means of frequency multiplication).

According to the present invention, through suitable choice of the layersequences and by using appropriate contacting technologies, the singlelight sources of the projection light source can be actuatedindividually. This means that imaging errors can be minimized withoutlosing the advantage of a considerably increased depth of focus comparedwith conventional LED projectors. In this situation the imaging can berealized by means of lenses situated very close to one another or acommon lens system, which means that the monolithically grown projectionlight source is particularly cost-effective and compact.

The invention furthermore relates to a method for producing a laserdiode arrangement comprising the following steps.

At least one semiconductor substrate is provided. A first single lightsource comprising a first laser stack, a first n-contact layer and afirst p-contact layer is subsequently produced by means of epitaxialgrowth. Then a first dielectric layer is deposited on the firstp-contact layer. An intermediate layer is deposited on the firstp-contact layer. A second single light source, comprising a second laserstack, a second n-contact layer and a second p-contact layer is grownepitaxially. Then a second dielectric layer is deposited on the secondp-contact layer. The two dielectric layers are subsequently removed inorder to expose contact surfaces. Contacts are deposited on the exposedcontact surfaces and on the exposed contact layer furthest away from thesubstrate. This method is particularly advantageous becauseself-adjusting exposure of the contact surfaces is possible in thissituation.

The dielectric layer, which serves as a passivation layer, can bedeposited over the entire surface and subsequently structured or canalternatively be structured using lift-off technology.

In a preferred development of the method, after the step of growing asingle light source and before the step of depositing a dielectric layeron a partial region of the p-contact layer the following steps arecarried out: Firstly, an insulation layer is grown on the contact layer.The insulation layer is subsequently partially exposed by means ofetching or lift-off. This development is preferably used whenincorporating a current limiting layer.

As an alternative to the method described above, the overall layer stackcan be grown entirely epitaxially. The contact surfaces are subsequentlyexposed by means of phototechnology and etching technology. The contactmetallization is then deposited and structured by means ofphotolithography or lift-off technology. The advantage of this method isthat it requires few epitaxy steps.

Laser light in laser diodes can propagate in index-guided and/orgain-guided fashion.

In a preferred development of the invention, the laser diode arrangementhas laser ridges which serve to guide the laser radiation. In thissituation, the active region is limited laterally to one strip byrefractive index jumps. The optical wave is guided in a waveguide. Thedesign of the waveguide can be achieved by means of different layerthicknesses and/or layer sequences. In this situation, differenteffective refractive indices result inside and outside the strip. Inorder to improve the electrical confinement, the contact is additionallydesigned as a strip. The advantage of index-guided laser diodes incomparison with gain-guided laser diodes is the low threshold current.By way of the width of the laser ridges it is possible to controlwhether only one mode is oscillating (ridge widths of less than about 2μm) or whether a multimode operation is taking place.

Only gain-guided systems are illustrated in the exemplary embodimentsdescribed in the following. Index-guided systems can however bedescribed in an analogous manner.

BRIEF DESCRIPTION OF THE DRAWINGS

Different exemplary embodiments of the solution according to theinvention will be described in detail in the following with reference tothe drawings.

FIG. 1 shows the flowchart for a first production process;

FIGS. 1.1 to 1.5 show the intermediate products of the first productionprocess from FIG. 1;

FIG. 2 shows the flowchart for a second production process;

FIGS. 2.1 to 2.5 show the intermediate products of the second productionprocess from FIG. 2;

FIG. 3 a shows a first exemplary embodiment of a layer sequence;

FIG. 3 b shows an exemplary embodiment of a layer sequence;

FIG. 3 c shows an exemplary embodiment of a layer sequence;

FIG. 3 d shows an exemplary embodiment of a layer sequence;

FIG. 3 e shows an exemplary embodiment of a layer sequence;

FIG. 4 a shows an exemplary embodiment of a laser light source;

FIG. 4 b shows an exemplary embodiment of a laser light source;

FIG. 4 c shows an exemplary embodiment of a laser light source;

FIG. 5 a shows an exemplary embodiment of a laser light source;

FIG. 5 b shows an exemplary embodiment of a laser light source;

FIG. 6 a shows an exemplary embodiment of a laser light source;

FIG. 6 b shows an exemplary embodiment of a laser light source;

FIG. 6 c shows an exemplary embodiment of a laser light source;

FIG. 7 shows an exemplary embodiment of a laser light source;

FIG. 8 a shows an exemplary embodiment of a laser light source;

FIG. 8 b shows an exemplary embodiment of a laser light source; and

FIG. 8 c shows an exemplary embodiment of a laser light source;

EXEMPLARY EMBODIMENTS OF LASER DIODE ARRANGEMENT

The same elements or elements of the same type or having the samefunction are identified by the same reference characters in the figures.The figures and the relative proportions of the elements represented inthe figures should not be regarded as to scale. Rather, individualelements can be represented exaggerated in size in order to enhancepresentation and for better understanding.

FIG. 1 shows a first flowchart for producing a laser light source. Thefirst production process can be subdivided into the steps S1.1 to S1.6.

In step S1.1, a semiconductor substrate 2 is provided with a bufferlayer 3. A single light source is grown epitaxially thereon. The singlelight source comprises a laser stack 30, a first n-contact layer 40 anda first p-contact layer 50. In the growth direction the laser stack 30consists of a first n-cladding layer 4, a first n-waveguide 5, a firstactive zone 6006 a, a first p-waveguide 7 and a first p-cladding layer8.

The result of step S1.1 is illustrated in FIG. 1.1.

In step S1.2, a first dielectric layer 53 is deposited on a partialregion of the first p-contact layer 50.

The result of step S1.2 is illustrated in FIG. 1.2.

In step S1.3, a first tunnel diode 9 is deposited on the first p-contactlayer 50. On this is grown a second single light source, comprising asecond n-contact layer 41, a second laser stack 31 and a secondp-contact layer 51. A second dielectric layer 54 is deposited on thesecond p-contact layer 51. In the growth direction the second laserstack 31 comprises a second n-cladding layer 10, a second n-waveguide11, a second active zone 6012 a, a second p-waveguide 13 and a secondp-cladding layer 14.

The result of step S1.3 is illustrated in FIG. 1.3.

In step S1.4, a second tunnel diode 15 is grown on the second p-contactlayer 51. On this is grown a third single light source, comprising athird n-contact layer 42, a third laser stack 32 and a third p-contactlayer 52. In the growth direction the third laser stack 32 comprises athird n-cladding layer 16, a third n-waveguide 17, a third active zone6018 a, a third p-waveguide 19 and a third p-cladding layer 20.

The result of step S1.4 is illustrated in FIG. 1.4.

In step S1.5, the first dielectric layer 53 and the second dielectriclayer 54 are removed.

The result of step S1.5 is illustrated in FIG. 1.5, wherein can be seenthe first exposed contact surface 59 a and the second exposed contactsurface 59 b.

In step S1.6, contacts (70, 71, 72) are deposited on the exposed contactsurfaces 59 a, 59 b and on the third p-contact layer 52.

The end result of the first production process is illustrated in FIG. 6a.

FIG. 2 shows a second flowchart for producing a laser light source. Thesecond production process can be subdivided into the steps S2.1 to S2.6.

In step S2.1, a semiconductor substrate 2 is provided with a bufferlayer 3. A single light source is grown epitaxially thereon. The singlelight source comprises a laser stack 30, a first n-contact layer 40 anda first p-contact layer 50. In the growth direction the laser stack 30consists of a first n-cladding layer 4, a first n-waveguide 5, a firstactive zone 6006 a, a first p-waveguide 7 and a first p-cladding layer8. A first insulation layer 55 is deposited on the first p-contact layer50.

The result of step S2.1 is illustrated in FIG. 2.1.

In step 2.2, a partial region of the first p-contact layer 50 is coveredwith a first dielectric layer 53. In addition, the first insulationlayer is exposed, whereby a recess 56 is formed in the first insulationlayer 55.

The result of step S2.2 is illustrated in FIG. 2.2.

In step 2.3, a first tunnel diode 9 is grown. On this is grown a secondsingle light source, comprising a laser stack 31 having a second activezone 6012 a and having a second n-contact layer 41 and a secondp-contact layer 51. On this is grown a second insulation layer 57. Apartial region of the second p-contact layer 51 is covered with a seconddielectric layer 54. In addition, the second insulation layer 57 isexposed, whereby a recess 58 is formed in the second insulation layer57.

The result of step S2.3 is illustrated in FIG. 2.3.

In step 2.4, a second tunnel diode 15 is grown. On this is grown a thirdsingle light source. The single light source has a third laser stack 32comprising a third n-cladding layer 16, a third n-waveguide 17, a thirdactive zone 6018 a, a third p-waveguide 19 and a third p-cladding layer20. On this is deposited a third p-contact layer 52.

The result of step S2.4 is illustrated in FIG. 2.4.

In step S2.5, the first dielectric layer 53 and the second dielectriclayer 54 are removed.

The result of step S2.5 is illustrated in FIG. 2.5, wherein can be seenthe first exposed contact surface 59 a and the second exposed contactsurface 59 b.

In step S2.6, contacts (70, 71, 72) are deposited on the exposed contactsurfaces 59 a, 59 b and on the third p-contact layer 52.

The end result of the second production process is illustrated in FIG. 6c.

FIG. 3 a shows an epitaxially grown layer sequence 1 wherein the tunneldiodes 9, 15 are arranged outside the cladding layers. This is a layersequence having so-called conventional polarity. In the growth directionthe n-doped semiconductor substrate 2 is followed by a buffer layer 3, afirst n-cladding layer 4, a first n-waveguide 5, a first active zone 6,a first p-waveguide 7, a first p-cladding layer 8, a first tunnel diode9, a second n-cladding layer 10, a second n-waveguide 11, a secondactive zone 12, a second p-waveguide 13, a second p-cladding layer 14, asecond tunnel diode 15, a third n-cladding layer 16, a third n-waveguide17, a third active zone 18, a third p-waveguide 19, a third p-claddinglayer 20 and a p-contact layer 21. FIG. 1 furthermore shows three laserstacks 30, 31 and 32. Laser stack 30 comprises the first n-claddinglayer 4, the first n-waveguide 5, the first active zone 6 for theemission of blue light, the first p-waveguide 7 and the first p-claddinglayer 8. Laser stack 31 comprises the second n-cladding layer 10, thesecond n-waveguide 11, the second active zone 12 for the emission ofgreen light, the second p-waveguide 13 and the second p-cladding layer14. Laser stack 32 comprises the third n-cladding layer 16, the thirdn-waveguide 17, the third active zone 18 for the emission of red light,the third p-waveguide 19 and the third p-cladding layer 20.

FIG. 3 b shows an epitaxially grown layer sequence 1001 wherein, incontrast to FIG. 1, the tunnel diodes 1009 and 1015 are arranged insidethe cladding layers. As in the previous FIG. 3 a, this is a layersequence having conventional polarity. With regard to the laser diodeswhich are formed from the laser stacks 1030, 1031 and 1032, thep-waveguides 1007, 1013, 1019 adjoin the upper sides of the active zones1006, 1012, 1018. In the growth direction the n-doped substrate 1002 isfollowed by a buffer layer 1003, an n-cladding layer 104, a firstn-waveguide 1005, a first active zone 1006, a first p-waveguide 1007, afirst tunnel diode 1009, a second n-waveguide 1011, a second active zone1012, a second p-waveguide 1013, a second tunnel diode 1015, a thirdn-waveguide 1017, a third active zone 1018, a third p-waveguide 1019, ap-cladding layer 1020, a p-contact layer 1021.

A first laser stack 1030 comprises the n-cladding layer 1004, the firstn-waveguide 1005, the first active zone 1006 and the first p-waveguide1007. A second laser stack 1031 comprises the second n-waveguide 1011,the second active zone 1012 and the second p-waveguide 1013. A thirdlaser stack 1032 comprises the third n-waveguide 1017, the third activezone 1018, the third p-waveguide 1019 and the p-cladding layer 1020. Asa result of the fact that in FIG. 2 the tunnel diodes are arrangedinside the cladding layers, the active zones are closer together. Thisenables the laser diode arrangement to have a lower height.

FIG. 3 c shows an epitaxially grown layer sequence 2001 wherein thetunnel diodes 2005 and 2011 are arranged outside the cladding layers.This is a layer sequence having inverted polarity. The layers facing thesemiconductor substrate 2002, which layers adjoin the active zones 2008,2014, are the p-waveguides 2007, 2013. The layers facing away from thesemiconductor substrate 2002, which layers adjoin the active zones 2007,2014, are the n-waveguides 2009, 2015. The layer sequence has a firstlaser stack 2030 and a second laser stack 2031. In the growth directionthe semiconductor substrate 2002 is followed by a buffer layer 2003, afirst n-cladding layer 2004, a first tunnel diode 2005, a firstp-cladding layer 2006, a first p-waveguide 2007, a first active zone2008, a first n-waveguide 2009, a second n-cladding layer 2010, a secondtunnel diode 2011, a second p-cladding layer 2012, a second p-waveguide2013, a second active zone 2014, a second n-waveguide 2015, a thirdn-cladding layer 2016, a third tunnel diode 2017, a third p-claddinglayer 2018 and a p-contact layer 2019.

FIG. 3 d shows an epitaxially grown layer sequence 3001 wherein thefirst tunnel diode 3005 is arranged outside the cladding layers andwherein the second 3010 and the third 3014 tunnel diodes are arrangedinside the cladding layers. As in the previous FIG. 3 c, this is a layersequence having inverted polarity. The first tunnel diode 3005 is anabsolute necessity because the substrate 3002 is n-type. The layersfacing the semiconductor substrate 3002, which layers adjoin the activezones 3008, 3012, are p-waveguides 3007, 3011. The layers facing awayfrom the semiconductor substrate 3002, which layers adjoin the activezones 3008, 3012, are n-waveguides 3009, 3013.

In the growth direction the semiconductor substrate 3002 is followed bya buffer layer 3003, a first n-cladding layer 3004, a first tunnel diode3005, a first p-cladding layer 3006, a first p-waveguide 3007, a firstactive zone 3008, a first n-waveguide 3009, a second tunnel diode 3010,a second p-waveguide 3011, a second active zone 3012, a secondn-waveguide 3013, a second n-cladding layer 3016 and a p-contact layer3017.

The first tunnel diode 3005 is necessary if the semiconductor substrate3002 is n-type.

The layer sequence has a first laser stack 3030 and a second laser stack3031.

FIG. 3 e shows an epitaxially grown layer sequence 4001. The layersequence is identical to the layer sequence 1001 in FIG. 3 a except thatcrystalline electrically insulating layers 4009, 4015 are grown on asintermediate layers instead of the tunnel diodes 9, 15.

The exemplary embodiments illustrated in the following in FIGS. 4 a, 5a, 5 b, 6 a, 6 b, 6 c, 7 are based on the layer sequence 1 from FIG. 3a. The exemplary embodiments illustrated in the following in FIGS. 4 b,4 c, 8 a, 8 b and 8 c are based on the layer sequence 4001 from FIG. 3e.

FIG. 3 a shows, as already established above, the epitaxial layersequence for conventional polarity. This means that in the case of thelaser diodes which are formed from the laser stacks 30, 31 and 32 thep-sides adjoin the upper sides, in other words on the sides of theactive zones 6, 12 and 18 facing away from the semiconductor substrate.The layers facing the semiconductor substrate 2 which adjoin the activezones 6, 12, 18 are n-waveguides 5, 11, 17. The layers facing away fromthe semiconductor substrate 2 which adjoin the active zones 6, 12, 18are p-waveguides 7, 13, 19.

All the exemplary embodiments shown in FIGS. 4 a to 8 c are purelygain-guided laser diode arrangements. Effects identical or at leastsimilar thereto can also be achieved in the case of purely index-guidedor gain-guided and index-guided laser diode arrangements.

All the exemplary embodiments shown in FIGS. 4 a to 8 c aremonolithically grown edge emitters. In the case of an edge emitter thelaser resonator runs in a plane parallel to the substrate. The laserlight is emitted from out of the drawing plane. Edge emitters can emitlaser light at high power levels on account of their long resonatorlengths of up to several 100 μm. Edge emitters are thereforeparticularly well suited for applications in laser projectionarrangements. Dielectric mirrors or simply the front and rear surfacesof a laser stack can be used as laser mirrors. In the followingexemplary embodiments, only arrangements are shown which use the frontand rear surfaces of a laser stack as laser mirrors.

FIG. 4 a shows an exemplary embodiment 10001 of a multi-color laserlight source having individually actuatable active zones 6, 12, 18. Thelaser diode arrangement comprises a semiconductor substrate 2 havingthree laser stacks 30, 31, 32 each having an active zone 6, 12, 18 andhaving two intermediate layers 9, 15. The laser stacks 30, 31, 32 andthe intermediate layers 9, 15 are grown monolithically on thesemiconductor substrate 2. The intermediate layers 9, 15 are arrangedbetween the laser stacks 30, 31, 32. The active zones 6, 12, 18 can beactuated separately from one another.

The active zones 6, 12, 18 are actuated by three separate n-contacts 60,61, 62 and three separate p-contacts 70, 71, 72. The first n-contact 60and the first p-contact 70 are used for separate contacting of thefirst, blue, active zone 6. The second n-contact 61 and the secondp-contact 71 are used for separate contacting of the second, green,active zone 12. The third n-contact 62 and the third p-contact 72 areused for separate contacting of the third, red, active zone 18.

With its associated active zone 6, 12, 18, each laser stack 30, 31, 32has laser diode 95, 96, 97. The first and the second intermediate layersare implemented by tunnel diodes 9, 15.

The active zones 6, 12, 18 are designed such that laser diodes 95, 96,97 from different laser stacks 30, 31, 32 emit electromagnetic radiationin wavelength ranges differing from one another. The first active zone 6is designed for the emission of blue laser light. The second active zone12 is designed for the emission of green laser light. The third activezone 18 is designed for the emission of red laser light.

In order for example to individually actuate the green active zone 12,current is applied to the p-contact (71) for green and the n-contact(61) for green.

The first laser diode 95 emits in the blue spectral range, the secondlaser diode 96 emits in the green spectral range and the third laserdiode 97 emits in the red spectral range. The active zone 6 for theemission of blue laser light is grown first so as not to negativelyinfluence the higher In concentration of the active zone 12 for theemission of green laser light by the subsequent epitaxy steps.

The vertical spacing between the laser diodes 95, 96, 97 from differentactive zones 6, 12, 18 is less than about 20 μm, preferably less thanabout 5 μm and especially preferably less than about 2 μm.

FIG. 4 b shows an exemplary embodiment 10002 of a multi-color laserlight source having individually actuatable active zones 6, 12, 18. Thestructure in FIG. 4 b is identical to the structure in FIG. 4 a exceptfor the intermediate layers. The difference consists solely in that inFIG. 4 b the intermediate layers 4009 and 4015 are designed as acrystalline electrically insulating layer. As an alternative to theabove, epitaxially grown, insulating layer 4009, 4015 it is alsopossible to produce an insulating layer by means of ion implantation.

Beneath each of the n-cladding layers 4, 10 and 16 lies a respectiven-contact layer 40, 41 and 42 with high n-doping. On these n-contactlayers 40, 41 and 42 are deposited the three n-contacts 60, 61 and 62. Arespective p-contact layer 50, 51 and 52 extends above each of thep-cladding layers B, 14 and 20. On these p-contact layers 50, 51 and 52are deposited the three p-contacts 70, 71 and 72. In order toindividually actuate the laser diode 95 for blue light, current isapplied to the first n-contact 60 and the first p-contact 70. Toindividually actuate the laser diode 96 for green light, current isapplied to the second n-contact 61 and the second p-contact 71. Toindividually actuate the laser diode 97 for red light, current isapplied to the third n-contact 62 and the third p-contact 72.

FIG. 4 c shows a layer sequence identical to FIG. 4 b, the onlydifference being the orientations of the contacts. In FIG. 4 b then-contacts 60, 61, 62 are situated on the opposite side of the layerstack in relation to the p-contacts 70, 71, 72. In FIG. 4 c then-contacts and the p-contacts are arranged on the same side of the layerstack. This configuration is particularly advantageous for placing twoor more laser diode arrangements close to one another. The laser diodes95, 96, 97 in turn emit in the blue, green and red spectral ranges.

FIG. 5 a shows an exemplary embodiment 10004 of a multi-color lightsource having individually actuatable active zones 5006 a, 5012 a, 5018a. A common p-contact 100 and individual n-contacts 60, 61 and 62 areprovided for the emission of blue, green and red light. The first activezone 5006 a is designed for the emission of blue laser light. The secondactive zone 5012 a is designed for the emission of green laser light.The third active zone 5018 a is designed for the emission of red laserlight.

In order for example to actuate the green emitting laser diode 5096 a,current is applied to the common p-contact 100 and the second n-contact61. The red emitting laser diode 5097 a does not light up if as a resultof greater losses in the case of the red emitting laser diode 5097 a thegreen emitting laser diode 5096 a oscillates first. The losses areadjustable by way of the indium concentration in the active zones.

FIG. 5 b shows an exemplary embodiment 10005. The arrangement isidentical to FIG. 5 a except that the sequence of the colors of theactive zones 5006 b, 5012 b and 5018 b has been changed. The firstactive zone 5006 b is designed for the emission of red laser light. Thesecond active zone 5012 b is designed for the emission of green laserlight. The third active zone 5018 b is designed for the emission of bluelaser light. A common p-contact 100 is also used in this exemplaryembodiment.

In order for example to individually actuate the green active zone 5096b, current is applied to the n-contact 61 for green and the commonp-contact 100. The blue laser diode 5097 b does not light up because onaccount of the greater band gap of the blue laser diode 5097 b the greenlaser diode 5096 b oscillates first and begins to lase.

FIG. 6 a shows an exemplary embodiment 10006 of a multi-color lightsource having individually actuatable active zones 6006 a, 6012 a, 6018a. A common n-contact 101 and individual p-contacts 70, 71 and 72 areprovided. The n-contact 101 is connected to the underside of thesubstrate 2. The common n-contact 101 is preferably designed as ametallic conductor.

In order for example to actuate the green emitting laser diode 6096 a,current is applied to the common n-contact 101 and the second p-contact71. In this situation, the blue emitting laser diode 6095 a would notoscillate because on account of the greater band gap the green emittinglaser diode 6096 a oscillates first and begins to lase.

FIG. 6 b shows an exemplary embodiment 10007. It is identical to thearrangement in FIG. 6 a except that the third active zone 6018 b isdesigned for the emission of yellow light. As already illustrated inFIG. 6 a, the first active zone 6006 b is designed for the emission ofblue laser light and the second active zone 6012 b for the emission ofgreen laser light.

FIG. 6 c shows an exemplary embodiment 10008. It is based on thestructure from FIG. 6 a. FIG. 6 c differs from FIG. 6 a in that a firstinsulation layer 55 is grown on the first p-contact layer 50 and asecond insulation layer 57 is grown on the second p-contact layer 51. Arecess 56 is provided in the first insulation layer 55, and a recess 58is provided in the second insulation layer 57. A first tunnel diode 9 isgrown on the structure comprising first insulation layer 55 and recess56. A second tunnel diode 15 is grown on the structure comprising secondinsulation layer 57 and recess 58. The insulating layers 55 and 57 withtheir respective recesses 56 and 58 are used for current constriction inthe buried layers. On account of the current spreading inside themonolithic layer stack it can be advantageous to incorporate currentconstriction layers inside the monolithic layer stack in order to adjustthe emission width of the single light sources based on the laser stacks30, 31 and 32. This is prerequisite for operating the light source 10008in monomode operation. In order to maintain clarity, no laser diodeshave been drawn in FIG. 6 c.

FIG. 7 shows an exemplary embodiment 10009 which is a multi-color lightsource having individually actuatable active zones 6, 12, 18. Theexemplary embodiment shows a two-dimensional structure of the laserdiodes. The laser diodes inside a laser stack 30, 31, 32 are actuatedjointly. Two laser diodes are produced in each active zone by means ofgain guidance. Blue emitting laser diodes 95 and 95 b are formed fromthe first active zone 6. Green emitting laser diodes 96 and 96 b areformed from the second active zone 12. Red emitting laser diodes 97 and97 b are formed from the third active zone. The two-dimensional laserdiode structure enables a high optical power density whilstsimultaneously reducing the loading on the facets. The laser diodes 95,95 b; 96, 96 b; 97, 97 b are moreover arranged horizontally, in otherwords parallel, with respect to the semiconductor substrate 2. Thehorizontal spacing between the laser diodes 95, 95 b; 96, 96 b; 97, 97 bis less than about 100 μm, preferably less than about 20 μm andespecially preferably less than about 5 μm. The geometric properties ofthe emission surface are also favorable. This permits the use of lesscomplicated optical imaging systems, in other words for example a simplelens or a simple lens system. In addition, better imaging propertiesresult. The formation of two or more laser diodes in an active zone isfor example advantageous in order to take account of the sensitivity ofthe eye or other requirements. A second green laser diode 96 b isprimarily a possibility here. It is thereby also possible to balance thediffering efficiency of laser diodes having different emissionwavelengths.

FIG. 8 a shows an exemplary embodiment 10010 having a layer stack 1 xand a layer stack 1 y. The layer stack 1 x is grown on a firstsemiconductor substrate 2 x. The layer stack 1 y is grown on a secondsemiconductor substrate 2 y. The arrangement of the layers on each ofthe two semiconductor substrates 2 x, 2 y corresponds to that of theexemplary embodiment 10003 from FIG. 4 c. Accordingly the n-contacts 61x and 62 x and the p-contacts 70 x, 71 x of the layer stack 1 x arearranged on one and the same side. The first n-contact 60 x is depositedon the side of the semiconductor substrate 2 x facing away from thelayer stack 1 x. The third p-contact 72 x completes the top of the layerstack 1 x.

The n-contacts 61 y and 62 y and the p-contacts 70 y, 71 y of the layerstack 1 y are likewise arranged on one and the same side. The firstn-contact 60 x is deposited on the side of the semiconductor substrate 2y facing away from the layer stack 1 y. The third p-contact 72 ycompletes the top of the layer stack 1 y.

GaN, AlN, InN or Si come into consideration as the first semiconductorsubstrate 2 x.

GaAs, GaP or Si come into consideration as the second semiconductorsubstrate 2 y.

A layer stack based on the AlInGaN material system is grown on the firstsemiconductor substrate 2 x. By preference, the first active zone 6 x isdesigned for the emission of blue laser light, the second active zone 12x for the emission of cyan colored laser light and the third active zone18 x for the emission of green laser light.

A layer stack based on the AlInGaP material system is grown on thesecond semiconductor substrate 2 y. By preference, the first active zone6 y is designed for the emission of yellow laser light, the secondactive zone 12 y for the emission of amber colored laser light and thethird active zone 18 y for the emission of red laser light.

As a result of the configuration described above, the two monolithiclayer stacks 1 x and 1 y can be arranged close to one another such thatthey exhibit a spacing in the region of a few μm. In this situation, thecontacts 61 x, 62 x, 70 x, 71 x of the layer stack 1 x point in theopposite direction to the contacts 61 y, 62 y, 70 y, 71 y.

This configuration produces minimally spaced laser diodes. Spacings inthe region of less than about 50 μm, preferably less than about 10 μm,especially preferably about 2 μm can be implemented. This holds true onthe one hand for laser diodes inside the first layer stack 1 x andinside the second layer stack 1 y. But the above spacings in the μmrange also hold true for the spacings between laser diodes from thefirst layer stack 1 x and the second layer stack 1 y. It is therebypossible to achieve an optimum projection with minimal imaging errors. Asimple lens system is moreover sufficient. By growing or arranging morethan three single light sources each having an active zone 6 x, 12 x, 18x, 6 y, 12 y, 18 y, in other words for example as described above, blue,cyan, green, yellow, amber and red, it is possible to enlarge the colorspace to be mapped. In order to maintain clarity, no laser diodes havebeen drawn in FIG. 8 a.

FIG. 8 b shows an exemplary embodiment 10011 having a firstsemiconductor substrate 2 x and a second semiconductor substrate 2 y. Afirst laser stack 30 having an active zone 6 which is designed to emitblue laser light is grown on the first semiconductor substrate 2 x. Onthis is grown a crystalline, electrically insulating layer 4009. Abovethis is grown a second laser stack 31 having an active zone 12 which isdesigned to emit green laser light. Grown directly onto the second laserstack 31A is second p-contact layer 51. Deposited thereon is a firstp-metallization 92. A solder layer 91 creates the connection to a redsingle emitter which has been grown separately from the first substrate2 x on the second substrate 2 y. This red single emitter is connected byway of a second p-metallization 90 with the solder layer 91. In otherwords, the red single emitter with the epitaxy layers, such as p-contactlayer 52, p-cladding layer 20, p-waveguide 19, active zone for theemission of red light 18, n-waveguide 17, n-cladding layer 16, n-contactlayer 42 and second substrate 2 y is connected face-down with the layersgrown on the first substrate 2 x. A passivation layer 80 and a thirdn-contact 62 are deposited on the second substrate 2 y.

The advantage of the arrangement 10011 consists in the following. Theactive zone 6 for the emission of blue laser light and the active zone12 for the emission of green laser light can be grown simply andcost-effectively on the first substrate 2 x, for example GaN. The activezone 18 for the emission of red laser light can be grown particularlysimply and cost-effectively on the second substrate 2 y, for exampleGaAs. Only after the epitaxial growth has taken place are the twomonolithic layer stacks connected to one another in electricallyconducting fashion and mechanically by means of the metallization layers92 and 90 and by means of a solder layer 91. A third p-contact 72 isdispensed with in this situation. Current is also applied to the p-sideof the “red” layer stack by way of the second p-contact 71.

The first p-metallization 92 comprises an alloy of Ti, Pt and Au.Titanium is used here as an adhesion agent. Platinum is used as adiffusion barrier. The solder 91 comprises AnSn or In. In order tomaintain clarity, no laser diodes have been drawn in FIG. 8 b.

A further advantage of the “face-down” structure, in particular in thecase of power lasers, is the improved heat dissipation.

FIG. 8 c shows an exemplary embodiment 10012 having a firstsemiconductor substrate 2 x and a second semiconductor substrate 2 y.The arrangement is identical to the arrangement from FIG. 8 b exceptthat an insulation layer 93 and a separate third p-contact 72 areprovided instead of the solder layer 91. This separate p-contact 72 isrequired because the insulation layer 93 is arranged between thep-metallization layer 92 for the layer stack 31 and the p-metallizationlayer 90 for the layer stack 32. The p-metallization 92 is optional andcan be used for additional current injection. The insulation layer 93has a thickness between about 50 μm and 200 μm, preferably about 100 μm.In order to maintain clarity, no laser diodes have been drawn in FIG. 8c.

The laser diode arrangement and the method for producing a laser diodearrangement have been described by way of illustration of the underlyingidea with reference to several exemplary embodiments. The exemplaryembodiments are not restricted here to particular combinations offeatures. Even though several features and implementations have beendescribed only in conjunction with a specific exemplary embodiment orindividual exemplary embodiments, in each case they can be combined withother features from other exemplary embodiments. It is likewiseconceivable to omit or add individual described features or specificimplementations in exemplary embodiments, insofar as the generaltechnical teaching remains implemented.

Even though the steps of the method for producing a laser diodearrangement are described in a particular sequence, it is thenunderstood that each of the methods described in this disclosure can becarried out in any other meaningful sequence, whereby method steps canalso be omitted or added, insofar as no deviation occurs from thefundamental idea of the described technical teaching.

LIST OF REFERENCE CHARACTERS

-   -   1 Layer sequence    -   2 Substrate    -   3 Buffer layer    -   4 First n-cladding layer    -   5 First n-waveguide    -   6 First active zone (blue)    -   7 First p-waveguide    -   8 First p-cladding layer    -   9 First tunnel diode    -   10 Second n-cladding layer    -   11 Second n-waveguide    -   12 Second active zone (green)    -   13 Second p-waveguide    -   14 Second p-cladding layer    -   15 Second tunnel diode    -   16 Third n-cladding layer    -   17 Third n-waveguide    -   18 Third active zone (red)    -   19 Third p-waveguide    -   20 Third p-cladding layer    -   21 p-contact layer    -   30 First laser stack    -   31 Second laser stack    -   32 Third laser stack    -   40 First n-contact layer    -   41 Second n-contact layer    -   42 Third n-contact layer    -   50 First p-contact layer    -   51 Second p-contact layer (green)    -   52 Third p-contact layer (red)    -   53 First dielectric layer    -   54 Second dielectric layer    -   55 First insulation layer    -   56 Recess in first insulation layer    -   57 Second insulation layer    -   58 Recess in second insulation layer    -   59 a First exposed contact surface    -   59 b Second exposed contact surface    -   60 First n-contact (blue)    -   61 Second n-contact (green)    -   62 Third n-contact (red)    -   70 First p-contact (blue)    -   71 Second p-contact (green)    -   72 Third p-contact (red)    -   72 b Third p-contact (yellow)    -   80 Passivation layer    -   90 p-metallization (red)    -   91 Solder layer    -   92 p-metallization (green)    -   93 Insulation layer    -   95 First laser diode (blue)    -   96 Second laser diode (green)    -   97 Third laser diode (red)    -   95 b Fourth laser diode (blue)    -   96 b Fifth laser diode (green)    -   97 b Sixth laser diode (red)    -   100 Common p-contact    -   101 Common n-contact    -   Layer sequence    -   1002 Substrate    -   1003 Buffer layer    -   1004 n-cladding layer    -   1005 First n-waveguide    -   1006 First active zone    -   1007 First p-waveguide    -   1009 First tunnel diode    -   1011 Second n-waveguide    -   1012 Second active zone    -   1013 Second p-waveguide    -   1015 Second tunnel diode    -   1017 Third n-waveguide    -   1018 Third active zone    -   1019 Third p-waveguide    -   1020 p-cladding layer    -   1021 p-contact layer    -   2001 Layer sequence    -   2002 Substrate    -   2003 Buffer layer    -   2004 First n-cladding layer    -   2005 First tunnel diode    -   2006 First p-cladding layer    -   2007 First p-waveguide    -   2008 First active zone    -   2009 First n-waveguide    -   2010 Second n-cladding layer    -   2011. Second tunnel diode    -   2012 Second p-cladding layer    -   2013 Second p-waveguide    -   2014 Second active zone    -   2015 Second n-waveguide    -   2016 Third n-cladding layer    -   2017 Third tunnel diode    -   2018 Third p-cladding layer    -   2019 p-contact layer    -   3001 Layer sequence    -   3002 Substrate    -   3003 Buffer layer    -   3004 n-cladding layer    -   3005 First tunnel diode    -   3006 First p-cladding layer    -   3007 First p-waveguide    -   3008 First active zone    -   3009 First n-waveguide    -   3010 Second tunnel diode    -   3011 Second p-waveguide    -   3012 Second active zone    -   3013 Second n-waveguide    -   3014 Third tunnel diode    -   3015 Third p-waveguide    -   3016 Second p-cladding layer    -   3017 p-contact layer    -   4009 First crystalline, electrically insulating layer    -   4015 Second crystalline, electrically insulating layer    -   1 x First layer stack    -   2 x First substrate (for example GaN)    -   3 x First buffer layer    -   4 x First n-cladding layer    -   5 x First n-waveguide    -   6 x First active zone (blue)    -   7 x First p-waveguide    -   8 x First p-cladding layer    -   4009 x First crystalline electrically insulating layer    -   10 x Second n-cladding layer    -   11 x Second n-waveguide    -   12 x Second active zone (cyan)    -   13 x Second p-waveguide    -   14 x Second n-cladding layer    -   15 x Second crystalline electrically insulating layer    -   16 x Third n-cladding layer    -   17 x Third n-waveguide    -   18 x Third active zone (green)    -   19 x Third p-waveguide    -   20 x Third p-cladding layer    -   30 x First laser stack    -   31 x Second laser stack    -   32 x Third laser stack    -   40 x First n-contact layer (blue)    -   41 x Second n-contact layer (cyan)    -   42 x Third n-contact layer (green)    -   50 x First p-contact layer (blue)    -   51 x Second p-contact layer (cyan)    -   52 x Third p-contact layer (green)    -   60 x First n-contact (blue)    -   61 x Second n-contact (cyan)    -   62 x Third n-contact (green)    -   70 x First p-contact (blue)    -   71 x Second p-contact (cyan)    -   72 x Third p-contact (green)    -   80 x Passivation layer    -   1 y Second layer stack    -   2 y Second substrate (for example GaAs)    -   3 y Second buffer layer    -   4 y First n-cladding layer    -   5 y First n-waveguide    -   6 y First active zone (yellow)    -   7 y First p-waveguide    -   8 y First p-cladding layer    -   4009 y First crystalline electrically insulating layer    -   10 y Second n-cladding layer    -   11 y Second n-waveguide    -   12 y Second active zone (amber)    -   13 y Second p-waveguide    -   14 y Second n-cladding layer    -   15 y Second crystalline electrically insulating layer    -   16 y Third n-cladding layer    -   17 y Third n-waveguide    -   18 y Third active zone (red)    -   19 y Third p-waveguide    -   20 y Third p-cladding layer    -   30 y First laser stack    -   31 y Second laser stack    -   32 y Third laser stack    -   40 y First n-contact layer (yellow)    -   41 y Second n-contact layer (amber)    -   42 y Third n-contact layer (red)    -   50 y First p-contact layer (yellow)    -   51 y Second p-contact layer (amber)    -   52 y Third p-contact layer (red)    -   60 y First n-contact (yellow)    -   61 y Second n-contact (amber)    -   62 y Third n-contact (red)    -   70 y First p-contact (yellow)    -   71 y Second p-contact (amber)    -   72 y Third p-contact (red)    -   80 y Passivation layer    -   5006 a First active zone (blue)    -   5012 a Second active zone (green)    -   5018 a Third active zone (red)    -   5006 b First active zone (red)    -   5012 b Second active zone (green)    -   5018 b Third active zone (blue)    -   5095 a First light-emitting diode (blue)    -   5096 a Second light-emitting diode (green)    -   5097 a Third light-emitting diode (red)    -   5095 b First laser diode (red)    -   5096 b Second laser diode (green)    -   5097 b Third laser diode (blue)    -   6006 a First active zone (blue)    -   6012 a Second active zone (green)    -   6018 a Third active zone (red)    -   6006 b First active zone (blue)    -   6012 b Second active zone (green)    -   6018 b Third active zone (yellow)    -   6095 a First laser diode (blue)    -   6096 a Second laser diode (green)    -   6097 a Third laser diode (red)    -   6095 b First laser diode (blue)    -   6096 b Second laser diode (green)    -   6097 b Third laser diode (yellow)    -   10001 Laser light source    -   10002 Laser light source    -   10003 Laser light source    -   10004 Laser light source    -   10005 Laser light source    -   10006 Laser light source    -   10007 Laser light source    -   10008 Laser light source    -   10009 Laser light source    -   10010 Laser light source    -   10011 Laser light source    -   10012 Laser light source

1. A laser diode arrangement comprising: at least one semiconductorsubstrate, having at least two laser stacks each having an active zoneand having at least one intermediate layer, wherein the laser stacks andthe intermediate layer are grown monolithically on the semiconductorsubstrate, wherein the intermediate layer is arranged between the laserstacks, and wherein the active zone of the first laser stack can beactuated separately from the active zone of the at least one furtherlaser stack.
 2. The laser diode arrangement as claimed in claim 1,wherein separate actuation of the active zones is provided.
 3. The laserdiode arrangement as claimed in claim 2, wherein separate actuation ofthe active zones by a common p-contact is provided.
 4. The laser diodearrangement as claimed in claim 1, wherein separate actuation of theactive zones by separate p-contacts is provided.
 5. The laser diodearrangement as claimed in claim 4, wherein separate actuation of theactive zones by a common n-contact (101) is provided.
 6. The laser diodearrangement as claimed in claim 1, wherein each laser stack with theassociated active zone has at least one laser diode.
 7. The laser diodearrangement as claimed in claim 1, wherein the intermediate layer has atunnel diode having a low ohmic resistance.
 8. The laser diodearrangement as claimed in claim 1, wherein the intermediate layer has aninsulator, in particular a crystalline electrically insulating layer. 9.The laser diode arrangement as claimed in claim 6, wherein the activezones are designed such that laser diodes from different laser stacksemit electromagnetic radiation in wavelength ranges differing from oneanother.
 10. The laser diode arrangement as claimed in claim 1, whereinthe laser diode arrangement has at least two light sources, formed fromthe laser stacks, having different semiconductor substrates.
 11. Thelaser diode arrangement as claimed in claim 6, wherein the verticalspacing between the laser diodes is less than about 20 μm, preferablyless than about 5 μm and especially preferably less than about 2 μm. 12.The laser diode arrangement as claimed in claim 1, wherein the layerfacing the semiconductor substrate, which layer adjoins the active zone,is an n-waveguide and the layer facing away from the semiconductorsubstrate, which layer adjoins the active zone, is a p-waveguide. 13.The laser diode arrangement as claimed in claim 1, wherein a currentshield is provided between two laser stacks.
 14. A method for producinga laser diode arrangement, comprising the steps of: providing at leastone semiconductor substrate; epitaxially growing a first single lightsource, comprising a first laser stack (30), a first n-contact layer anda first p-contact layer; depositing a first dielectric layer on apartial region of the first p-contact layer; epitaxially growing anintermediate layer on the first p-contact layer epitaxially growing atleast one second single light source, comprising a second laser stack, asecond n-contact layer and a second p-contact layer; depositing a seconddielectric layer on a partial region of the second p-contact layer;removing the at least two dielectric layers by means of etching orlift-off in order to expose contact surfaces; and depositing contacts onthe exposed contact surfaces and on the exposed contact layer furthestaway from the substrate.
 15. The method as claimed in claim 14, whereinafter the step of growing a single light source and before the step ofdepositing a dielectric layer on a partial region of the p-contact layerthe following steps are carried out: growing an insulation layer on thecontact layer; exposing the insulation layer by etching or lift-off. 16.A laser diode arrangement comprising: a semiconductor substrate, havingat least two laser stacks based on the material system AlInGaN, eachhaving an active zone and having at least one intermediate layer,wherein the laser stacks and the intermediate layer are grownmonolithically on the semiconductor substrate, the intermediate layer isarranged between the laser stacks, the active zone of the first laserstack can be actuated separately from the active zone of the at leastone further laser stack, each laser stack with the associated activezone has a laser diode, the active zones are designed such that laserdiodes from different laser stacks emit electromagnetic radiation inwavelength ranges differing from one another, the layer facing thesemiconductor substrate, which layer adjoins the active zone, is ann-waveguide and the layer facing away from the semiconductor substrate,which layer adjoins the active zone, is a p-waveguide, or vice versa,and a current shield is provided between two laser stacks.